all of the sudden my folder icons disappeared on OS X Yosemite.
It looks like this:
These are all folders, they are not missing their icon in finder tho, only in the primary view.
Best Answer
First of all a quick reboot might fix your problems. If that does not work, you could try relaunching finder. Apple icon → Force Quit → Finder → Relaunch. If that does not work you could try deleting the Icon Cache. Go to Terminal, which you can just search for, or go to Applications → Utilities → Terminal. Paste exactly these commands in one at a time.
Do note that when you put in a sudo command, you must put in your password once. The characters do not appear when typing them, so don't worry.
If this does not work, you should do a complete restore of the Mac. Look up tutorials online, but make sure to do a backup of your Mac with Time Machine or a cloud based service.
The window may be using one of the "Arrange By" options. Disclosure triangles are not available in "arranged" views. If that's the case, you can choose View → Arrange By → None or press ^ control⌘ command0.
On Mojave the concept is called "Group" instead of "Arrange". Keyboard shortcut is the same. Menu item is found as follows: View → Use Groups.
Best Answer
First of all a quick reboot might fix your problems. If that does not work, you could try relaunching finder. Apple icon → Force Quit → Finder → Relaunch. If that does not work you could try deleting the Icon Cache. Go to Terminal, which you can just search for, or go to Applications → Utilities → Terminal. Paste exactly these commands in one at a time.
Do note that when you put in a sudo command, you must put in your password once. The characters do not appear when typing them, so don't worry.
If this does not work, you should do a complete restore of the Mac. Look up tutorials online, but make sure to do a backup of your Mac with Time Machine or a cloud based service.
Good luck!